1. Field of the Invention
The present invention relates in general to mineral recovery wells, and in particular to an apparatus and method for supporting a tensioned tubular assembly.
2. Brief Description of Related Art
Tubular members such as wellbore risers are often placed under tension. A riser, for example, can extend from a subsea wellhead upward to a drilling platform. It is often necessary to place a certain amount of tension on the riser. The tension can be applied by, for example, latching the riser into place on the wellhead, and then drawing it upward through an opening in a drilling platform until the riser is subject to the desired amount of tension. The riser can then be latched into place by a latching mechanism on the drilling platform to maintain the tension.
The tension latch provides the connection between the riser tension joint and tensioner system on a floating platform. It sits atop the tension conductor, which is located on a deck of the platform. As the riser is made up, all segments of the riser system must pass through a rotary or a spider. The limitation on the riser is the greatest outer diameter (“OD”) on the riser must be less than the inner diameter (“ID”) of the spider. The same limitation is also present at the tensioner, the largest OD must be able to pass through the tension latch. Conventional methods of tensioning and latching a riser have numerous problems.
With conventional tension latches, it can be difficult to center the riser assembly within the opening of the drilling platform or within the latching mechanism. If the riser is offset within the opening, then it can be difficult, or even unsafe, to latch the riser in position with conventional latching mechanisms. Those conventional latching mechanisms can include segmented dogs that can engage the riser assembly. It is difficult to engage in the riser with segmented dogs when the riser is offset. Engaging the riser with the segmented dogs can also require personnel to be present on the drilling platform to operate heavy equipment. Safety can be an issue any time personnel are operating heavy equipment, especially in close proximity to a tensioned riser. Furthermore, heavy equipment must be lifted and operated in order to engage the riser with the segmented dogs, which can further present safety issues. Additionally, the conventional latching mechanisms have a large number of moving parts. Those moving parts can be expensive and can have mechanical failures.
Another problem with conventional latching techniques is that they are not able to prevent upward movement of the riser assembly. Under some circumstances, risers can be subjected to upward force that can cause the riser assembly to thrust upward from the drilling platform. Conventional risers are not suited to provide downward support to prevent a riser assembly from thrusting upward.